1. Field Of The Invention
The present invention relates to pressure actuated flow control valves in conjunction with inflatable packers and grouting systems on offshore oil platforms, and more particularly, to a pressure actuated control valve which sequentially inflates a series of packers or sequentially grouts a series of annuli in response to first and second pressure actuating means.
2. Description of the Prior Art
On offshore drilling platforms, it is necessary to secure the legs of the platform to the ocean floor, and a number of methods have been developed to do this. In the typical procedure, a plurality of jacket legs are set on bottom. Each jacket leg is flanked by a plurality of skirt jackets or sleeves which are attached to the jacket leg and set on bottom at substantially the same time. The jacket leg is a structural member of the offshore platform or tower that extends from the sea bottom to the working deck above sea level. The skirt jacket or sleeve is a jacket or sleeve which is structurally attached to the jacket leg, but extends only partially from the sea bottom toward sea level After the jacket leg and skirt sleeves are set on bottom, piles are driven through each into the sea bed. The pile is smaller in diameter so that an annulus is defined therearound. A leg pile is any pile placed through the leg jacket, and a skirt or sleeve pile is any pile placed through the skirt jacket or sleeve.
A similar structure is found on the more recently developed tension leg platforms. With these platforms, a template is positioned on the ocean floor with a floating platform located thereabove. Anchoring members extend from the platform to the template to hold the platform in its operating position. The anchor members are always in tension and allow some side-to-side movement of the platform, although the platform is prevented from rising and falling with the swells in the ocean. The tension leg platform template has a plurality of skirt sleeves. There are no jacket legs. As with a conventional offshore platform, piles are driven into the skirt sleeves such that an annulus is defined between each pile and the corresponding skirt sleeve.
Inflatable packers are positioned in the annulus at the bottom of each jacket leg and skirt sleeve and are inflated once the piles are in place. The inflated packers bridge the gap between the pile and jacket leg or skirt sleeve, sealing the lower end of the annular space formed therebetween. Grout is then pumped into the annular space between the pile and jacket leg or skirt sleeve to fill the annular space and displace the water therein. Generally, the grout enters a few feet above the packer.
In the most common previous method, a separate inflation line for each packer was run from the surface, and two grout lines, a primary and a secondary grout line, were run from the surface to each annular space that was to be grouted. Such a plurality of lines is expensive, and the likelihood of damage to the lines as the platform is set in place is increased because of the number. Also, the amount of time and expense in installing, identifying and testing the lines during construction of the platform is quite high.
One solution to the problem of multiple lines is the Unitrol.RTM. manifold grout/inflation system manufactured by Halliburton Services which can reduce the number of surface lines by 50% to 67%. By using an inflation control valve, a single surface inflation line can be used to inflate two packers. A single surface grout line can be used to grout up to three annular spaces by using a sleeve-type grout valve. However, even this system has some limitations. Balls are dropped through the surface grout line to operate the grout valve, and this requires that the surface line must have bends no greater than 30.degree.. Also, each surface line must be pigged prior to setting the platform in place to insure that the balls can reach the grout valves. Further, having one surface grout line to grout three annular spaces still results in a relatively large number of surface lines, although this is a reduction over the previously known methods.
The pressure actuated flow control valve of the present invention solves all of these problems and is designed to use only one surface line, referred to as the main grouting line, for grouting any number of annular spaces and one surface line, referred to as the main inflation line, for inflating any number of packers desired. In fact, by combining the valve used to inflate the packers and the valve used to grout the annular spaces, a single surface line may be used which can be connected to first an inflation source and then a grout supply. The only additional requirements for the control valve of the present invention is that one or two relatively small pressure actuating lines must be run to a pressure source, preferably at the surface. These lines transmit pressure to operate the control valve.